Video files (MPEG-4 with H.264 compression) with appropriate file extensions (.mp4, .m4v, .mov). For best results with iPod, Apple recommends using MPEG-4 with H.264 compression with the following specifications:

You can also use iTunes U to distribute Portable Document Format (PDF) and electronic publication (ePub) files. ePub files must pass ePubCheck 1.0.5, include only files listed in the manifest, and use UTF-8/16 characters. For more details, read the complete ePub specification at
http://www.idpf.org/specs.htm. PDF and ePub files appear in iTunes U and the iTunes U library with a book icon. To open a PDF or ePub file, download the file and double-click the file. iBooks or another reader is required (download the free iBooks application from the App store). You cannot preview a PDF or ePub file in iTunes U.

If you host your content on a server using an SSL URL scheme (https), be sure to set up a valid certificate. If iTunes U cannot obtain a verifiable certificate the request fails. If you cannot set up a valid certificate, switch your content to a server using a non-SSL URL scheme.

If you are using QuickTime to create and edit video content, Apple recommends that you export your videos by choosing “Movie to iPod” from the Export pop-up menu in QuickTime Pro. For more information, see
http://www.apple.com/quicktime/.

Notes:

Some MP3 audio files, specifically ID3 version 1.x tagged files, have known issues displaying track artwork information. To use specific artwork with these audio files, Apple recommends either converting the files to MP3 files tagged as ID3 version 2.4 or converting the files to the AAC file type format (.m4a).

iTunes U does not support the downloading of WAV or AIFF file formats on the iPod, iPhone, or iPad.

Due to video file profile level requirements, iTunes U might not play some files on the iPad without re-encoding the files. For more information, see the iPad audio playback and TV and video requirements at
http://www.apple.com/ipad/specs/.